Going the wrong way

On the way back home from a one-day spring skiing trip in Jasper, I saw a flock of birds flying south. I thought they're supposed to fly north in spring. My brother was there too and he is my witness.

Today on the way home from work, I saw a flock of birds flying north. Again, I would've expected them to fly the other way. I didn't have any witnesses with me, but shortly after that, I saw another flock of birds flying south, so if my sense of direction is messed up, there was still at least one flock of birds going the wrong way. A little while after that, I saw several flocks of birds quite close together, all flying north, and then another lone flock flying north.

I wonder what makes these birds go the wrong way. Maybe they got tired and thought, I saw a lake back there. I'll turn around and rest there. Or maybe they read a Yellowknife weather forecast in Fahrenheit and they thought it was in Celsius. Any other far-fetched explanations?